You can look it at 1 of 2 ways I see it. 1. you can walk away from the deal and try to find another one that works better, if you walk away from the deal you could always tell the owners to call you if they want to come down to numbers that work. 2. you do the deal at hand and live rent free allowing you to build up more capital for future purchases and build equity on the house assuming your market goes up.

Is it better to have a team of agents, or build up a great relationship with just one realtor?

Have you found it better/wiser, in hindsight, to slowly build up your portfolio?  

If you get the word out enough- you should start find deals and if you build up your buyers list at the same time , you may be able to wholesale some of the deals that you cannot take advantage of.

My main goal is to build up a $100K monthly passive income by doing subject to's and lease options or other low/no money down strategies that would put me in control of property (I'm a long way off).

As I work to build up credit I will network and get to know the area and build my knowledge of flipping/ investing.

I think that is a great way for me to build up some some needed cash flow!

Most wholesalers only need one to three good buyers, and you can find them in a week, you dont need to spend a year networking to build up a list of 50-100 potential buyers.

I also want the chunks of income that flips generate so that I can build up a cash reserve to self-fund my deals at some point.  

Keep at it and it will build up.